Riflemen are potentially the highest damage dealing unit in the game, depending on how close the target is to the riflemen and if you get any lucky crits, the riflemen are a top tier unit. If it does not crit and you are far away from the enemy and you run out of ammo before you get in close then the riflemen are terrible. Riflemen are the best boss killers in the game, just repeat the battle until you get a string of lucky crits and you will see the boss melts into nothing.

Research upgrades for Riflemen are unlocked at academy level 1

Tier 1: Fitness training – Flat health increase, leads to silver Riflemen
Tier 2: Combat Training – Flat damage increase, leads to scope, which increases Riflemen chance to get a headshot is increased by 1% (for a total of 4%)
Tier 3: Garrison Stockpile – increase ammo capacity of Riflemen while stationed in the garrison, leads to Advanced Agility Training which increases Riflemen attack speed by 10%
Tier 4: Basic Fitness Training – Bonus +% health for Riflemen, leads to Gold Riflemen
Tier 5: Convalescence – Reduces healing time of Riflemen by x%, leads to Garrison Recovery, which reduces healing time of garrisoned Riflemen by 40%
Tier 6: Advanced Fitness Training – Increase health of riflemen by x%, leads to Full Metal Jacket, which increases headshot damage from 50x to 100x damage.
Tier 7: Garrison Training – Increase Riflemen’s health and damage by x%, leads to Field Training: Tundra, which provides +20% health and damage to Riflemen while fighting on snowy battlefields
Tier 8: Training Discipline – Reduces the cost to produce Riflemen by x%, leads to brutal efficiency which reduces rare resource cost of producing a Riflemen by 20%
Tier 9: Elite Combat Training – Increase the damage of Riflemen by x%, leads to weapons Research, which increases Rifleman damage by 20%
Tier 10: Advanced Convalescence – Reduces healing time of Riflemen by an additional x%, leads to more garrison recovery, for a total of 100% recovery speed of garrison troops.
Tier 11: Extra Ammo – Increases ammo carried by Riflemen by x%, leads to Elite Agility Training, which gives Riflemen 20% increases attack speed.
Tier 12: Elite Fitness Training – Increases health of Riflemen by x%, Leads to Regroup which increases troop size of Riflemen to 12 up from 10.